Abstract:
Seagrass are the only marine angiosperm that adapted to the harsh marine
environment. Sediments provide suitable substrate for the seagrass. Thus
sediment characters are crucial factors which govern the growth and the
distribution of the seagrass. Seagrass meadows are vital ecosystems which
enhance the fish production as well as a tourist attraction. The facts finding
sites were Ahangama, Dickwella and Dondra, located in the Southern coast
of Sri Lanka which are famous for the fisheries and tourism. The species
composition and the coverage of these seagrass meadow was estimated
using Saitobe Atobe method (1970). Sediment sieve analysis was conducted
and Total Organic Carbon (TOC) was measured using standard chemical
methods. The highest seagrass cover was recorded from Ahangama seagrass
meadow with three seagrass species, Thalassia hemprichi (33.39%),
Syringodium isoetifolium (19.39%) and Halodule uninervis (7.78%).
Dondra was the mono species seagrass meadow includes Thalassia
hemprichi (24.63%). Halodule uninervis (54.21%) was the prominent
species in Dickwella meadow with Thalassia hemprichi (4.79%). Fine sand
particles showed positive correlation (r = 0.304) and the amount of mud
particles in the sediments showed negative correlation (r = -0.049) with the
species richness of the seagrass beds. Ahangama, Dondra and Dickwella
observed high levels of fine sand. However, seagrass bed in Dondra
revealed the highest amount of mud with high TOC. Therefore, research
revealed that seagrass ecosystems are highly influenced by higher amount
of fine sand particles and lower amount of mud with TOC. Hence, the
seagrass sediments analysis is an appropriate method to measure the health
of the ecosystem.
